The invention relates generally to methods and devices for human surgery, and in particular these methods and devices may be useful for spinal surgery. More particularly, certain embodiments of the invention relate to devices and methods for treating injuries, defects or surgical procedures associated with the intervertebral disc.
Injuries to the human spine and subsequent pain are one of the most prevalent debilitating conditions affecting the human population. For many of those affected, no position can ease the pain or discomfort associated with spinal injuries or deformities. Such spine related pain can lead to decreased productivity due to loss of work hours, addiction to pain-killing drugs, emotional distress, and prolonged hospital stays. The economic impact of such problems is significant. One common cause for many instances of chronic pain is the bulging, or herniation of the intervertebral disc.
The intervertebral disc is made of two parts, a tough collagen outer layer, known as the annulus fibrosus (hereinafter also referred to as “AF” or “annulus”), and a soft central core known as the nucleus pulposus. The annulus fibrosus is composed of numerous concentric rings or layers of fibrocartilaginous tissue. Fibers in each ring cross diagonally, and the rings attach to each other with additional radial fibers. The rings are thicker anteriorly (ventrally) than posteriorly (dorsally). The nucleus pulposus (hereinafter also referred to as “NP” or “nucleus”) is a gelatinous material, which forms the center of the disc. The discs tend to vary in size and shape with their position in the spine. The nucleus pulposus is composed of a loose, nonoriented, collagen fibril framework supporting a network of cells resembling fibrocytes and chondrocytes. This entire structure is embedded in a gelatinous matrix of various glucosaminoglycans, water, and salts. This material is usually under considerable pressure and is restrained by the annulus.
A tear or weakening in the layers of the annulus fibrosus portion of the disc can allow the soft center portion of the disc (the nucleus) to leak out of the annulus, alternatively, the weakened annulus may simply bulge. A ruptured disc may allow the leaking nucleus propulsus material to press up against a spinal nerve root or spinal cord, causing pain, numbness, tingling and/or weakness in a person's extremities. Herniated discs may occur at any level of the spine, but are more common in the lumbar area, followed in frequency of occurrence by the thoracic region and cervical region. Weakening or tearing of the annulus fibrosus may also result in bulging of the annulus fibrosus due to pressure of the nucleus pulposus against the annulus. The bulging tissue may also impinge upon the nerve root or spinal column, causing pain.
The traditional surgical method for treating a damaged, bulging, or herniated disc involves tissue removing procedures to relieve the impingement of the annulus fibrosus or the nucleus pulposus from the surrounding nerves. The procedure is commonly known as a discectomy, and consists of the removal of at least a portion of the disc; it may be performed in an open procedure, a minimally invasive procedure, or an endoscopically assisted procedure. These procedures generally result in a large defect of the annulus fibrosus and in a certain percentage of cases, may lead to progressive degradation of the disc, both nucleus pulposus and annulus fibrosus, lysthesis of adjacent vertebral bodies, stenosis of the nerve canals and increases in related pain symptoms. A means of mechanically and/or biologically repairing the annulus fibrosus may delay or prevent this degeneration cascade of the disc.
Newer technologies and procedures, such as nucleus replacement with injectable or solid prosthetic nucleus devices may also result in a breach in the otherwise coherent annulus fibrosis. In these cases, it is desirable to mechanically close, or otherwise repair the defect in the annulus created to insert the prosthetic material and prevent such material from leakage and extravasation.
The annulus fibrosis (AF) of the intervertebral spinal disc is a lamellar configuration of collagen layers intended to maintain the soft viscous internal nucleus propulsus (NP), provide for motion and linkage of the adjacent vertebral bodies (VB). Certain degenerative or pathologic changes may occur either within the NP which can lead to over stress of the AF and subsequent damage to or tearing of the AF. If left untreated, herniation of the NP may occur, most importantly, the herniation may progress posteriorly toward the spinal cord and major nerve roots. The most common resulting symptoms are pain radiating along a compressed nerve and low back pain, both of which can be crippling for the patient. The AF may also be torn through traumatic injury, which can lead to progressive degenerative changes and herniation or ultimately listhesis of the adjacent VB.
Herniation may be caused by, or be the result of weakening in the AF. Secondary to physiologic changes of the AF or NP, the AF may weaken and protrude from its normal anatomic space, similar to an air bubble bulge in a car tire, or in more severe cases, the AF may tear and allow extravasation of the NP contents to the surrounding anatomy. Symptoms may arise when the herniation or leakage of the NP impinges on the nerve root or spinal cord. There are therapies currently utilized for treatment of the herniation of a vertebral disc, and the resultant pain, starting with conservative therapies such as bed rest and pain medicines, to more invasive therapies, such as epidural injections, open or minimally invasive discectomies or aggressive therapies, such as complete discectomy and fusion of the disc space and adjacent vertebrae.
The prior art describes various procedures and devices for repairing damage to the vertebral disc. The prior art describes repairing a herniated disk by various means, including prosthetic implants, and stressed members. For example, in U.S. Pat. No. 6,805,695, Keith et al. disclose devices and methods of reinforcing an annulus of the disc by introducing a circumferential reinforcement member around the annulus of the disc, or through the annulus and nucleus of the disc.
In U.S. Pat. No. 6,371,990, Ferree discloses an apparatus and method for repairing annular tears and the prevention of further annular tears. Ferree seeks to control vertebral motion by augmenting the annulus with an implant, thereby minimizing the opportunity for annular tears. The augmenting implant is described as being a mesh that may be stapled into the interior of the annulus.
Ferree also discloses in U.S. Patent Application 2004/0097980 an expandable material to fill a defect in a disk, and that the material may be anchored to the annulus with respect to the void filled. In an embodiment, the anchors are described as penetrating through the outer wall of the disc and serve to hold the flexible implant material in place.
Yeung discloses in U.S. Pat. No. 6,530,933 a method and apparatus for herniated disc repair using resilient fastener elements that are implanted and spring back to an original shape to apply tension through gripping elements to hold tightly to the annulus. In an alternative embodiment, the annulus repair technique utilizes a suture affixed to a dumbbell shaped rod to serve as an anchor. The anchor is placed against the outside surface of the annulus, and the suture extends across the interior of the vertebral disc through the nucleus propulsus and out the other side of the disk, such that tension may placed against the disc to repair the hernia, and the tension may be maintained through the use of a washer and suture locking element, such as a knot. With this alternative embodiment, a sealing material may optionally be placed underneath the washer.
In U.S. Pat. No. 6,592,625, Cauthen describes annular repair or reconstruction by insertion of a collapsible patch into the subannular space, whereupon the patch expands to fill the gap and seal off the opening from the escape of nucleus material. Cauthen describes his device as being useful to restore integrity after damage or discectomy to alleviate a herniated vertebral disc; Cauthen does not obviate the need for the discectomy procedure to repair a herniated disc.
In U.S. Pat. No. 6,224,630, Bao describes the repair of an intervertebral disc using an expandable porous material that is inserted into an aperture, and subsequently becomes more permanently secured as the ingrowth of tissue into the pores is actively facilitated. Bao creates a device having a tamponade effect where the swelling of the material provides securement and does not describe a more secure mechanical anchorage using a rigid component in combination with a tissue regenerative material.
The prior art also describes various methods for sealing a percutaneous closure, for example, Kensey et al. in U.S. Pat. No. 5,545,178 describe a system for sealing a puncture made through skin and having a tract extending through to underlying tissue. The puncture closure system consists of an anchor introduced into the underlying tissue and having a filament attached thereto, the filament extends out from the puncture, and facilitates the introduction of a plug material into the tract, whereupon tension is maintained through the use of a holding member. Kensey et al. does not describe the sealing of multiple sites through the employment of a single device, nor is the employment of multiple anchors or plugs on a single filament described.
The prior art does not describe a device wherein the device may be capable of being implanted arthroscopically, among other methods known in the art, and is arranged to prevent the escape of nucleus propulsus from a defect in the annulus, while providing supporting and secured sealing means in a single device, and the device may be capable of preserving normal annulus geometry.
Accordingly, there is a need for a device capable of meeting these and other objectives, wherein the device provides support and secure sealing means for a defect as well as the ability for cellular infiltration and subsequent repair occurring in or created in the annulus fibrosis. Furthermore, there is a need for a device capable of preserving or restoring normal annulus geometry (e.g., repairing a herniated disc), wherein there is support and secured sealing provided at each point of penetration or defect in the annulus.
It is the intent of this invention to overcome these and other shortcomings of the prior art.